Multiple unit floating dry dock



July'10, 1945. F. R. HARRIS MULTIPLE UNIT FLOATING DRY nocx Filed April9, 1943 4 Sheets-Sheet 1 INVENTOR FREDERIC R. HARRIS y 10, 19 5. F. HARRIS 2,37 ,90 I MULTI EPLE UNIT FLOATING DRY DUCK Filed April 9. 1945 .4 Sheets-Sheet 2 -FIG. In. FIG. lb. 3 2/ INVENTOR FfiEDfP/C A fll/QP/S A'ITORNEY July 10, 1945. F. R. HARRIS MULTIPLE UNIT FLOATING- DRY DOCK.

Filed April 9, 1943 4 Sheets-Sheet 3 n'h'H INVENTOR FREDfR/C R. HARRIS BY I M fjm ATTORNEY ATTORNEY 7 MI I III INVENTOR FREDER/C R- HARRIS 4 Sheets-Sheet 4 F. R. HARRIS I MULTIPLE UNIT FLOATING DRY DOCK I Filed April 9, 1943 July 10,1945.

Patented July 10,

UN IT ED STATES PATEN r tomes This invention relates to floating dry docks, and has for its principal object to provide an exceedingly mobile and highly serviceable dock made of separate parts which can be propelled or towed about expeditiously from place to place; and are capable of being assembled 'for use in one location andthen readily divided and transferred to another as need may arise.

In its preferred form the invention embodies an improved floating dry dock comprising individual units, each of which has a pontoon hull and sections of side or wing walls, and which can be dispatched separately to the chosen site and there assembled withthe other units; or detached for separate removal to anew location; where the units will be reassembled in the same manner as before.

, In principle the invention relates to a dock comprising units, each of'which has the side or wing Wall sections on the pontoon hull notflxed but movable; so that they can befolded or laid down horizontally to diminish wind resistance when the hull moves about; and easily raised to uprightposition. Thus the hull is rendered more seaworthy and can be transferred from place to place at higher speed and with less expenditure of power. j

The invention is well adapted to provide what is termed; in naval operations, an advance base deck; that is, a dock to be available in waters which are not very remote from the sphere of naval actiom-to enable quick repairs to be made Another feature of the invention resides in the bow and stem construction of the individual hulls, which are made with bottoms that rise progressively higher toward the ends of the hull so that the free water surface area within the units decreases as the pontoon hull is pumped, out. The bottoms are shaped so that the free water area in each u'nit begins to decrease before the loaded dry dock rises to a height that just lifts a ship therein clear of the water. Each pontoon hull is preferably made with a central transverse buoy ancy chamber which alines with similar chambers in the other units; and in combination with track is preferably provided on both of the com.-

plete wing walls of the assembled dock.

wi l A further object of the invention is to provide neck when an individual unit is equipped to go to damaged or crippled warships; because the hull having ship characteristics. Each pontoonhull has a bow and stern of reduced width, and preferably pointed; and carries its. own power generating apparatusand propulsion equipment for driving the unit through the water as a ship.

The units are placed side by side to make the -to. sea; and moved later to the top of thewall section of another unit'when the units are to be assembled to set up the dock.

An additional feature of the invention is the 3m methodby which the wall sections are folded or complete dock; that is, the longtiudinal axis of each separate pontoon hull extends. transversely of the assembled dock. Means are provided on raised by controlling the buoyancy of the sections and the pontoon hull to which they are connected.

sections on the adjacent pontoon hulls when connecting the individual units to one another.

Other objects, features and advantages of the invention will appear or be pointed out as the specification proceeds.

In the drawings forming a part hereof, in which the same reference charactersdenote the same parts in all the views,

the stresses imposed on the drydock whenioaded. 55 F gu e 1 is aside elevation, on a small'scale,

showing one unit of a dry dock embodying this invention;

Figures 1a and 1b illustrate fastening means for the wall sections when vertical; and show how the sections are released for lowering;

Figure 2 is a view similar to Figure 1, but show ing the dry dock unit with the side wall sections folded down on the pontoon deck in their seagoing position;

Figure 3 is a front view, partly broken away and on an enlarged caleyof the dry dock unit shown in Figure 2;

Figure 4 is a longitudinal sectional view, on the line 44 of Figure 3, showing the progressive rise in the pontoon bottom toward the end of the pontoon; I Figure 5 is a top plan view, on a reduced scale, showing the manner in which a number of individual units are brought together side by side to make the complete dock;

Figure 6 is an enlarged end view of one of the units shown in Figure 5-conne'cted with adjacent and the inside framework are not part of the invention of this case, but are fully set-forth in my companion application, Serial No. 497,784,.

are crane tracks 29. The decks 28 are air-tight and water-tight so that the pontoon hulls can never be sunk entirely.

Figure 2 shows the sections 2| and 22 folded own on the deck of the pontoon hull 20. This s' their sea-going position. A pilot house 80 is located on the upper side ofthe wall section 2| units that are mostly broken away in the illustration;

Figure 7 is a side elevation of two units, one of which is submerged, in position for transferring a crane from the pontoon deck of one unit to the top of the wall section of. the submerged unit;

Figure 8 is a top plan view of the dry dock units shown in Figure '7;

Figures 9 and 10 are enlarged sectional views through the one type of engaging means for sean end view of a diflerent form of engaging means when the dock unit is to be used as a ship. This pilot house is preferably removed before the sections are swung up into the operative-position shown in Figure 1. Provision may be made for locating the pilot'house on a support outside of the wall section 2|, when the latter isin'uprightposition.

Each hull 20 has anchors 3| supported by anchor chains that extend through hawser holes I in thebow and stern of the hull:

3.5 are supplied with power from machinery in the Figures 11 to 15 are, diagrammatic side elevations illustrating a novel method by which the win wall sections are raised and folded;

Figure 16 is an enlarged detail view of the room 21 of the chamber through a'Diesel-engine electric drive. The rudders, are controlled from the pilot house 30. The engines, the transmission devices between them and the propellers, and the connections from the pilot house 30 to the rudhinged'connection between a wing wallsectio'n and its associated pontoon;

' Figure 17 is a sectional view on the line |'|-|1= of Figure 16; and

Figures 18 and 19 are respectively a side and a ,top view of means for admitting water to the wall ders are not shown herein, as they are not a part of this invention.

When the forward wall section 2| is down in folded position, it overlaps the crews quarters 26 and the portion of the wall section beyond the" deck 28 at what is the upper end when the section is raised, forms a compartment 34 that is used as a captains cabin and radio room. Access between the radio room and crew's quarters can side or wall sections 2| and 22. These wall sec- .50 be had through an enclosed passage or hatchtions are joinedto the pontoon hull by hinges 23 along the lower inside edges of the wall sections. The upright position of the wall sections 2| and 22, shown in Figure 1, is the position that they occupy in the assembled dock. when standing thus, the wall sections are all firmly secured to the hulls outside of the hinges 23, to insure against accidental folding or dropping of the sec;- tions when the dry dock is in use. Hooks, fastening bolts. or any other suitable means are indicated in Figure 1a, consisting for example-of bolts in flanges II on the sections, to screw down into suitable holes in beams I9 on pontoon hulls 20, and held by nuts on their ends,

As illustrated in Figures 6 and 8, fo'r example, both ends of each pontoon 'a re vertical, and the outline of the vertical extremities is approximately-Y-shaped. The exterior surface between the arms ofthe Y is plane or flat; outside'of the' Y it is curved, and in each vertical longitudinal plane from the center of the ends to the upper I Aands of the arms of the Y, "the curve becomes longer and higher till it :extends over the entire distance between bottom and deck. (See Figure 4). The shape of the hull: and theends thereof go Although each pontoonbot'tom, level along way 35 that opens through the pontoon deck. The entrance to both hull and wall section can of course be closed when the-latter is lifted, and the passageway itself removed or withdrawn inside the wall or hull. This feature is not a part of the invention of this case, but is fully described in my application Serial No. 482,375 for patent on a Pontoon unit for floating dock filed of even 3. Each hull 20 is pointed near the bottom and for a distance equal to about one-half the height of the hull, the upper'part of the bowjandstern are made with a generally vtriangular flat, end surface. I This construction does not materially affect the sea-worthinessfof the units in towing or self-propulsion.

aavaooe hull. As the pontoon hull is pumped out, and the dock rises higher in the water, the free water area 4| contracts in such a way that progressive pumping adds no further buoyancy to the ends of the hull, but concentrates the additional buoyancy efiect nearer to the center, where the ship load is concentrated.

This feature of reducing the free water surface area within each pontoon hull in such a way that buoyancy'is added toward the center of the hull as the dock rises to its position of maximum load,

. is describedin my patents, Nos. 2,291,076 and 2,291,077, issued July 28, 1942. By increasing the buoyany nearer the center as the dock rises to its position of maximum load, the stresses on the dock are reduced and the dock may be of lighter construction.

With the present invention the reduction of the free ,water surface area is of particular importance in practice, because of the extent of the pontoon hulls beyond the wing wall sections. This construction increases the span ofthe pontoon hull beyond that of a conventional deck of equal capacity in which the hull of the pontoon does not extend beyond the outer faces of the side walls.

Figure 5 shows a number of identical dock units 20 positioned side by side and connected together to form a complete dry dock. A dock of any desired length can be made by increasing the number of separate units.

The manner in which the units are connected together is shown in Figures 6 and 10. There are tapered socket members 44 on the side of each hull 20, and a similar socket member on the side of each wall section. Tapered heads 45 on the near side of the next adjacent dock unit, hull and wall section, fit into the socket members 44 and align the individual units withone another. The same devices unite the other sides of these units to the next unit. 7 Connector plates 46 on the outer faces of the respective wall sections arejoined together by tie plates 41, which may be detachably fastened to the connector plates, but-are preferably secured by welding, When welding and it becomes necessary to separate them. the tie plates 41 are cut apart with a torch. It will be observed that these engaging devices between the adjacent units, as well as the fastening provided by the connector plates. are widely spaced in a vertical direction to provide the dock with maximum strength against sagging or hogging stresses.

Figures 100. and 10b show a different type of fastening or engaging devices, consisting of re taining members fixed at the sides of the hull and wall sections of the units. When these mem-' bers engage, a member 44a receives a head 45".,

or retaining elements 44d held on the ends of the members 44a by suitable bolts. Thus it iseasy to effect the removal of any of the units 2): out 01' the line as illustrated in Figure 5'for self-docking on the other units. and repair or cleaning. The

hinges 23 of the wall sections on the unit are simply dismantled and all other connections removed between the pontoon hull of a unit and its wall sections 21 and 22, which are now secured to the wall sections of the units at each side. The plates 44d are taken off, the hull shifted to pull the members Ma and heads45a free; and the hull without its wall sections can then be fully withdrawn by pulling it from under the side walls. Later it can be reinstalled or even wholly replaced. For the same purpose the devices '44 and 45 may be removable, if desired.

Although the wall sections on adjacent units do not have their sides in contact with one another, the crane tracks as along the tops of the walls are fastened together by connecting members to f the wing walls of the assembled dry dock. A'crane 48 on each of the dry dock wings is capable of reaching at least one-half way across the dry dock.

the dry dock units are connected together by the former having a horizontal. slot 44!) with undercut edges 0. The member 45a has a shape like a short length of steel rail, with base. web and and the slots 4412 may have expanded or flaring ends to facilitate the entrance of the heads of theimembers 45a. Engagement is accomplished by movement of any hull lengthwise when these head; the heads may be tapered at the ends;

engaging devices are aligned. The members of When the wall sections 2| and 22 are folded down into sea-going position, each of the cranes 4 48 is carried on the deck of one of the pontoon hulls 20 on tracks 49 extending across the pontoon deck between the folded wall sections, as shown in Figure 2. The crane 48 is indicated in broken lines.

When the dry dock is. being assembled, and it is necessary to transfer the crane 48 to the top of a wall section. the transfer is done as illuspose, tapered heads 45 are provided on the side of the pontoon hull 20 and the upper portion of a When the wing section receiving said crane. the tapered heads 45 are engaged in the socket members 44, the wall section and unit can be held together by a swivel bolt 53 on the wall section. for example, that swings into a slot 54 in a hook 55 extending from the hull 20. A- nut 55 threaded on the free end of the swivel bolt 53 can be screwed further up on the bolt to secure the wall section to the pontoon hull 20 while the crane is being transferred from the pontoon deck to the top of the said wall section. V

Figure 8 shows the relative positions of the floating pontoon hull and the submerged pontoon hull when in position for transferring the crane as shown in Figure 7. It will 'be evident that if thecrane 48 where to be transferred from the deckv of the pontoon hull 20'- to the top. of the other wall section on the submerged pontoon hull 20, the latter would be merelyshifted lengthwise of itself until the other wall section occupied the right position. In this way cranes can be mounted on both track 28, as indicated in Figure 5. v

' Each wall section will have flues 51 opening through the deck 28 and the top for escape and entrance of air from the water space in the wall sections, below the decks"; and necks or conduits 58 on the inner face near the bottom for sections. Flues 51 do not communicate with the spaces above decks 28.

Figures 11 to 15 illustrate the method by which I the wall sections are raised. In Figure 11 the pontoon is shown with the sections 2| and 22 in their lowered or folded, sea-going position. When it is desired to raise the bow section 2 l, for instance, into an upright position, it is first released from any connections with the pontoon deck that would prevent aiming at the hinges 23, and all openings that would admit water to any space in the pontoon or the wall section used by the crew are closed. Necks 68 of course are open. The pontoon hull 20 is "then flooded until both ends are below the water level so, as shown in Figure 12. Water is allowed to run into the hull in such wise that the bow of the pontoon hull 2o suitable kind. The necks 58 are more fully shown is submerged for a considerably greater depth than the stem. The water also enters the section freely through the necks 58. As soon as the pontoon hull begins to sink the section 2! begins to swing up, because of its buoyancy, to the position shown in Figure 12. As the bow sinks deeper, the water rises in the section 2!, and the center of gravity of this section and the water therein shifts forward. As soon as the center of gravity reaches an "off-center" position; that is, moves into a vertical plane between the hinge and the how, the section 2! ill be over-weighted forward a: the hinge and settle into upright position as in Figure 13. No forces other than gravity and buoyancy are needed. But if desired the operation may be assisted by a pull on a cable 58" attached to a capstan (not shown) on the pontoon hull and to the top of the section 2|.

The water in the hull 20 .is now pumped out until the pontoon hull rises to the position shown in Figure 13. The section 2| is then fastened to the pontoon deck to prevent accidental folding, and the water in it flows out through the necks 58. Next the section 22 is-released from the pontoon hull so that it is free to swing on its hinges movement about the hinges 23 are disconnectedand the pontoon hull 20 is submerged into substantially the position shown in Figure 14, with both ends under water and the stern lower than the bow. This at once causes the section 22 to tilt forward or inward. To control the section, valves in the necks 58 are opened, but not so much as when the section was lifted; and its fall is checked. It then comes down slowly to the deck, being cushioned by the water forward of its hinges. Otherwise its drop would be too rapid. By means of the valves in the necks 58, the shift of the center of gravity of the section 22 toward thebow till it crosses a vertical line;

through the hinge 23, is nicely regulated. Also, a cable 82 and a capstan tol pull the section 22 to the right may be employed, but is really not needed. .At the start all openings that might admit water, except as required, are closed as before.

The ports or ducts 51 in the tops of the sections may be left open or provided with closures of any in Figures 18 and 19. Apipe length 59 in the form of a horizontal elbow is fixed to the section and unltedat its outer end by a ball-joint 59' to another elbow pipe 80, having one endformedfto constitute part of the ball-joint 59'. The axis of this joint should preferably be in line withthe axis of the hinges, the pins for which are engaged .by bearing plates or lugs 6|. The pipe length 80 is united :by a ball joint 59a to a pipe length 60a, which may be secured to the pontoon deck and contain a valve 601). These valves may be of any proper design and arranged to be controlled by connections indicated in outline only at 60c, inside the hull and leading, for instance, to points in the compartment or quarters 26. Such connections may be mechanical or electrical or may include an airline, and can be made .by any one of ordinary technical skill. Swivel-joint conduits or piping of this general design are well known.

The connections for flooding and pumping out are not shown herein, but are fully disclosed and defined in the claims of my app a n ria 482,374 for patent on Floating dry dock and pumping apparatus, filed of even date herewith. But each pontoon unit has inlet and discharge ports in the lower part of its hull connected by conduits with valvesto the various compartments of the hull outside of the chamber 25, and pumps structed that it permits minor adjustment of the position of the section with respect to the pontoon .deck. The hinge 1, made up of plates or.

bearing lugs 6| that are connected to and extend from the inner face of the section at the bottom,

and other plates or hearing lugs 62 connected with the deck of the pontoon hull 20. A link 82 extends between the plates GI and 62 and is connected with these plates by pins 64 and 85. The link .63 has a recessed keyway 66 in which fits a key 61. The key 81 has upper flanges 68 that fltinto side recesses of the keyway 68 and lower flanges 89 thatengage undercut guides" secured to the pontoon deck. The flanges 68 and 69 of key 61 are convergent, making the key tapered, as shown in Figure 17; and the link 63 of hinge 23 can be raised or lowered by driving the key 67 to the right orJeft respectively, in

.Figure 17. By thus moving the key 61, each section may be raised or lowered along its hinged side to adjust the alignment of any section with other wall sections.

Opening through the pontoon deck is a port ll (Figures 1a and lb), in line with a port I2 in the bottom of each wall section when the latter is vertical. Thus the inside of the wall sections are put into communication with the pontoon hull 213111 can be flooded and pumped out through the to connect the wall sections with the pontoon compartments beneath it. When the wall sec- A -manyof these ports are used as needed secured over the ports. They are opened when the wall sections are raised, so that-the sections and'pontcon can be flooded and pumped out together. The crews quarters in the pontoon are then connected through passageways to thespaces. in the wall sections above the decks 28, as fully disclosed and in my application for patent on a Pontoon unit for a floating dry dock,

aforesaid.

On the deck of each pontoon null (Figures 1a and lb) at bow and stem are fixed beams id, to support the wall sections along the four edges of the bottom thereof. These beams have flanges at the top to be engaged by the bolts I8 which secure the wall sections in upright position. When the sections are to be raised, packing or gasket material l9f (Figure 16) may be laid on the tops of the beams to make a leakproof jqint between them and the wall sections; and at one point or more under each section the beams may a has a single pontoon hull, movable wall sections have an opening 13, with a screw plug I4, to ad- 'mit air under the wall sections when they are to be lowered. The plugs 14 are then screwed out. If desired one or more pipenecks I5 (Figure 1a) can be added to connect each well section with the inside of the pontoon hull; particularlycompartments between those directly below the wall sections and the chamber 25. These necks allow air and water to circulate when the hulls and wall sections are flooded or emptied. They can easily be removed. Necks '55 are only used and removed when The deck is also provided with air vent valves l8, beneath yokes 19, having bearing openings 80.

Springs 8| hold these valves closed. Air can thus escape when water is admitted to flood the pontoon hulls. For sea-going positions of th'e wallsections, the valves are not-in place and the openings are temporarily plated shut. These pipes l1 and vent valves are more fully described in my application covering the Floating dry dock and pumping apparatus aforesaid.

A dry dock of this design can be setup for use at one place and then taken apart and removed to another location and set up again. The units can either propel themselves by connection of the pumping engines, not shown, with the propellers 32, or be towed.

The invention has been described in its preferred embodiment, but changes and modifications can be made, and some features of th'e 'invention can be used without others.

Having described my invention, what I believe to be new and desire to secure and protect by Letters Patent of the United States is:

l. A floating dry dock made up of separate units, each of which has a ship form at its ends and bears transverse wallsections on its deck near bow and stem, means for pivotally connecting said sections to the deck, so that they can be laid down or stood upright thereon, and means for connecting the units together side by side to form the complete dry dock alignment.

with said sections in 2. A unit for a dry dock including a hull of"- attached to each hull, each section being substantially as long as the width of the hull and having its ends flush with the sides thereof, and arranged to be laid down on the hull or stood upright to provide wall sections adjacent opposuch a level that the free water surface within the hull decreases in area as the water is pumped out.

6. A dry dock unit with a hull having a bottom which is of virtually uniform depth along its 1011'- gitudinal center line but rises progressively higher laterally from said center line adjacent both ends of the unit and to such a level that the watersurface within the hull decreases in area as the unit is pumped free of water, the hull also having a centrally located buoyancy chamber therein.

7. A dry dock unit including a pontoon h'ull having a deck,-a wall section thereon, and hinge means having an axis extending transversely of the hull connecting the section to the pontoon hull so that the section may be raised to stand on said deck or lowered to lie thereon.

8. A dry dock unit including a pontoon hull, a.

wall section thereon, hinge means connecting the section to the hull, and means for adjusting the hingemeans to effect minor changes in *the position of the section with respect to the hull.

9. The method of folding a wall section upon a dry dock unit that has a pontoon hull and a hollow wall section movably connected thereto, said method comprisin the sinking of the pontoon hull until a substantial part of the section to be folded is under water, flooding the section in the course of sinking as it changes position by buoyancy, unbalancing the section, and lowering it on the deck of the hull.

10. The method of rearing the wallsection of a dry dock'that has a pontoon hull and a hollow wall section movably mounted thereon and resting on its deck, said method comprising the sinking of' the hull with the wall section free to swing upward, flooding the section, and raising the hull and allowin the wall section to settle down on the-pontoon in upright-position.

11. The method of getting the movable wall section of a dry dock unit intoposition on the deck of the unit, which comprises sinking the unit and pulling the section partly under water. allowing the section to move by its own buoyancy, weighting the lower portion-of the section, and

settling the section into stable position by forces including the action of gravity.

12. A dry dock comprising units, each of which has a pontoon hull with a deck and wall sections adjacent the opposite ends-of the deck, said sections having their ends flush with the sides of the position'of said link. 14. A dry dock pontoon hull with the hull, crane-supporting tracks on the deck 01 one unit and extending entirely across some,

wall sections thereon, said sections having hinged means connecting them to the hull, said means comprising a link, bearing lugs on the section and the hull to which the link is pinned at its ends, thelink having a recess in one edge, a tongue engaging the recess, and guide members for movably securing the tongue to the hull, the tongue being tapered for adjustment of said means.

15. The method of lowering a hollow wall section reared upon a dry dock unit that has a pontoon hull and the hollowwall section pivotally connected thereto, said method consisting in sinking the hull until a' substantial part of the section to be folded is under water, and tilting th section over by the action of its own buoyancy, flooding the section during sinking and then raising the pontoon hull to unbalance the section and lower it by gravity on the deck thereof.

16. The method of rearing the hollow wall section of a dry dock that has a pontoon hull and the hollow wall section pivotally connected thereto and resting on its deck, said method comprising, the sinking of the hull with the wall section free to swing upward, thus tilting the section as said h'ull sinks, and then raising the hull and allowing the wall section to settle down on the pontoon by its own weight in upright position.

17. The method of gettin the two wall sections of a dry dock unit into position on the deck of the unit, to which they have pivotal connection, which comprises sinking the unit till one section is partly under water, allowing it to move by its own buoyancy and weighting the lower portion of said section, then raising th unit and settling the section into" stable position by forces including the action of gravity; and repeating said steps to set the other section.

'18. A dry dock unit comprising a single pontOOn hull, with a wall section substantially as long gsthe beam of the hull and having its ends ush with the sides thereof movably connected to the deck thereof adjacent the lower end to be laid down on the deck or placed upright thereon,

munication with the inside oi the wall section/ 20. A dry dock unit comprising a pontoon hull with a deck, a wall section movably mounted on the hull, a conduit attached to the lower part of the section, said conduit having jointed parts one oi which is afllxedto the deck, and a controlling valve in said fixed part.

21. A dry dock comprising pontoon units to be aligned to form the dock, said units having means for securing them together comprising a retaining member with a head thereon, a receiving retaining member having undercut slots for said head, and plates for closing the ends of saidslot when the head is engaged within the slot.

22. A dry dock comprising-pontoon units to be joined to form the dock, said units having engaging means to hold them in alignment, said means comprising a socket member and a head to enter same, and a swivelled bolt to prevent separation of said units.

'23. A single dry dock pontoon unit having a deck, a wall section substantially as long as the beam of the hull and having its ends flush with the sides thereof movably mounted on the deck, beams having flanges to support the section and means for engaging the section and said flanges to hold the section in position, said unit being of ship form and extending beyond said wall section. Y

24. A dry dock pontoon unit having a hull and a wall section thereon, beams on the deck for supp rting the section, said beams having openings and removable closures for said openings, the beams encompassing a closed space through which the interior of the wall section may be connected to the inside of said hull.

25. A dry dock unit comprising a pontoon hull with a deck, a wall section with hinged connec- 40 tion thereto, a conduit attached to the lower the said hull being of ship form and extending beyond said wall section.

19. The dry dock unit according to claim 18, in which the section and the deck have openings which register when the section is upright, putting the inside of the pontoon hull into compart of the-section and comprising a joint in line with the pivot of said hinged connection, said conduit being secured to the deck and controlling valve in the conduit.

26. A dry dock unit including a pontoon having a deck, a wall section thereon, and hinge means the axis of which extends transversely of the pontoon,,for movably mounting the section on the deck so that the section can be lowered to rest on the deck, or raised to stand upright thereon across said pontoon.

27. A dry dock unit including a pontoon hull, a wall section thereon, hinge means connecting the section to the hull so that the section can be raised to stand upright or lowered tone on the deck, and mechanical connections between the hull and section remote from hinge means for controlling the movement of the section.

28. A dry dock unit comprising a hull, a wall section, hinged means for connecting the wall section to the hull to be laid down or stood upright thereon, and connections between the hull and said section remote from said hinge means to control the movement of the section.

4 FREDERIC R. HARRIS. 

